Peripheral and coronary blockages are caused by deposits of fatty substances, e.g., cholesterol, cellular waste products, calcium and fibrin (a clotting material in the blood) along the walls of blood vessels. Combinations of the foregoing are referred to herein generally as forms of plaque. Conventionally, narrowed blood vessels are widened or reopened by mechanical means such as angioplasty or atherectomy. These are invasive procedures. With atherectomy plaque is actually removed to enable less impeded blood flow. Atherectomy may be effected with a catheter system comprising a cutter blade for separation of the deposits, a system for dispersing the cut material, and an imaging system to guide catheter movement or aid in the cutting process. Generally, angioplasty and atherectomy are costly and complex procedures which create potential risks to the welfare of the patient. Moreover, the effectiveness of such procedures is limited, e.g., for treatment of coronary disease or blood vessels in the extremities. Nonetheless, because the build-up of deposits along the inner linings of vascular cavities causes life threatening medical problems, the benefits of using these methods are often seen to outweigh the risks. Yet, it remains desirable to provide a completely non-invasive technique which is effective, economical and without potential risk to the welfare of the patient.